Method of obtaining oxids of nitrogen from atmospheric air.



F. l. DU PONT.

METHOD 0F OBTAINING oxlns 0F NITROGEN FRoM ATMOSPHEWC Am.

APPLICATION FILED SEPT. 28, l9\2. 1,147,150. Patented July 20, 1915.

2 SHEETS-SHEET l,

F. l. DU PONT.

METHOD 0F OBTAINING OXIDS 0F NITROGEN FROM ATMOSPHERIC AIR.

APPLICATION FILED SEPT. 28. 1912.

1, 1 47, 1 50. J Patented July 20, 1915.

2 SHEETS-SHEET 2.

z ED STATES FRANCIS I. nu PONT, or' eToN, DELAWARE.

METHOD OIF OBTAINING OXIDS 0F NITROGEN FROM ATMOSPHERIC AIR.

Specification of Letters Patent.

Patented July 2o, 1915.

Application led September 28, 1912. Serial No. 722,789.

To all whom t may concern Be it known that I, FRANCIS I. DU PONT, a

citizen of the United States, residing at Wilmington, county of New Castle, and State of Delaware, have invented a new anduseful Improvement in Methods of Obtaining Oxids of Nitrogen from Atmospheric Air, of which the followin is a full, clear, and exact description, re erence being had to the accompanying drawings, which form a part of this specication.

The methods now generally used for obtaining oxids of nitrogen from atmospheric air, are uneconomical, in that the heat generated by the arc, including that which is necessary to actually effect the combination, is largel or wholly lost.

The o ject of my invention is to eiect the result with more economy than heretofore, and to that end, speaking generally, I have devised a process wherein the air is compressed, an electric arc passed therethrough and the air thus heated allowed to do useful work while expanding; the process bemg conducted in such a way that I can avail myself of a very tangible percentage of the totalv heat generated 1n the process.

More specically, my invention may be defined in different ways, and is so defined in the claims appended hereto.

In the preferred embodiment of my mvention definite quantities of the mixed gases are successively and independently highly heated and simultaneously expanded, and simultaneously with the heating and expansion the heat, or a very tangible percentage of it, is converted into mechanical energy by causing the expanding air to perform useful work. The gases are allowed to expand, without the use of a special cooling agency, during the application of heat and subsequent thereto; the heat is converted into mechanical energy during the entire expansion of the gases; and the mechanical energy thus obtained is utilized to subsequently exhaust the charge, and to aid in compressing and supplying heat for a new charge.

carrying out my invention, I may use a caloric engine similar to a 4-cycle gasolene engine, in which theinitial movement of the iston draws in air through `an inlet valve. ghe next movement of the piston compresses the air, the inlet valve being closed. By appropriate arran ement,the circuit from a source of electric supply is closed momentarily, and when broken, an arc is established which contlnues during a certain proportion of thedownward stroke. This arc heats the airin the cylinder intensely hot and the expansion of this air, under the influence of the heat, furnishes the motive power for driving the piston. At the same time that this is taking place, oxids of nitrogen are formed in the cylinder. The reverse action of redecomposition, which is one of the diiliculties in the production of oxids of nitrogen, is prevented, in a very great measure, by the cooling, d ue to the fact that the heat is converted into mechanical energy. Thus the heat, instead of producing a result detrimental to the process, is recovered as mechanical energy and may be again converted into additional electrical energy, which may be used in the process. vThe piston continues to the end of its stroke. On the return of the piston on the second revolution, y

an exhaust is opened which allows the 4air with the formed oxids of nitrogen to escape and they may 'be led to the point of utilization or converted into useful products.

I have shown in the accompanying drawings two sets of apparatus in whichmy improved 4process may be carried out, that shown in Figure 1 being the earlier of the two, while that shown in Fig. 2 isl of later development and resents certain advantziiges in the way o structure, as well as of e ectiveness and certainty of operation.

Fig. 1 is an elevation, partly 1n section, of one form of apparatus. Fig. 2 is a similar view of theother form of apparatus. Fig. 3 is a detail elevation of the contact device of Figl 1 and Fig. 4.- is a similarview of the contact device of Fig. 2.

Referring first to the apparatus of Figs. 1 and 3: a are the cylinders, b the pistons, c5 the inlet valves controlled by cams o, d `and e electrodes, f the switch cams designed to connect the terminals with the electrodes, it the exhaust valves controlled by cams g.

is a generator having connections from its terminals j and k with the electrodes d and e.

l, m, y and e are insulating joints which prevent electrical contact between the parts of the machine carrying electrodes d `and the parts carrying electrodes e. Any other method of preventing short circuiting around the two. electro es may be adopted by the skilled electrician.

The switch cam f is designed to connect the terminals with the electrodes d and e once in every two revolutions.

n isthe ily wheel.. Initially the engine is started by turning the iy wheel, but, taking it that the'engine is in motion, the cycle is as follows: Beginning with the piston at its high point, the electrodes d' and e are in contact but with no current passing because the cam is not in contact position. In the downward movement of the piston, the cam o holds the inlet valve c open and the cylinder fills with air.. On the return movemen't of the piston, the cam o closes inlet valve c and the air is compressed and the current is turned on by the cam f so that when the two electrodes d and e come in Contact for an instant, and part again, and an arcis established which continues during a portion of the next (downward) movement of the'piston.. The duration of this arc can be regulated by the shape of the cam f as may be determined by best practice. However, two thirds of the length of the stroke is a suitable duration. As stated, this heats the air intensely and thus enables the air to act expansively to drive the piston down. At the same time that this takes place, oxids of nitrogen are formed. The cooling of the air, due to the expansion, prevents, to a large extent, the action of redecomposition. After breakin the arc the piston travels the rest of the distance down the cylinder, and thel air 4which has been4 heated by the arc expands, having a proportion of its heat converted into mechanical energy. At this point the piston returns upon the second revolution, when the cam g opens the exhaust valve h land allows the air, together with the oxids of nitrogen which have been formed, to escape into a conduit which leads them to the apparatus in which. they are designed to be utilized, or converted into useful products. The exhaust valve h remains open during the backward movement of the piston, after which it is immediately closed and the operation just described is repeated.

The process may be operated in Aone of two ways. yThe generator i may have an excessive capacity and mechanical energy may be supplied to the system by turning the shaft from an outside source of mechani- ,cal energy, or the' engine may have excesslve power and additional current may be vsupplied to the wires g and 7'.

In the drawing, for the sake of simplicity, I have shown the lower electrode in metallic Contact with the connecting rod, crankn and shaft of the engine, and while the rocess would work this way, I am per ectly f aware that it would notbe good engineerevery other revolution.

Lirama all, but to maintain insulation up to the 4point of the electrodes themselves.

- s is permanently connected'with the other pole of the generator through the base of the apparatus and the wire 1". This apparatus presents several advantages over that of Fig. 1. First, as hereinbefore stated, it is desired to maintain the arc during about two-thirds of the stroke of themoving electrode, or about one third of the revolution of the crank shaft, which is about what would be necessary to allow properly for working the air expansively..` The six cylinder arrangement thus permits a continuous consumption of current, in that each cylinder uses the current for one-third of Second, the ratio of the amount of air in the cylinders actually heated to a high temperature in the arc to the amount of the air in the cylinders not so heated is considerably larger than in the apparatus of Fi. 1, thereby substantially adding to the e ciency of the apparatus. Third, by making the cylinder in the form of a tube composed of insulating material, no arc will form between the electrodes and the wall of the cylinder and thus it is absolutely insured that the air shall be heated to the degree required. If a current of very small amperage be used, the tube may be made of glass, but if the amperage be increased, I prefer to make the tube of silica.- A good working current'would be a, current of from two to ten amperes and from 3500 to 5000 volts. The operation of this apparatus, as well as the process carried out thereby, is the same as that of Fig. 1.

It will thus be seen that the preferred form of my invention exhibits novel characteristics of the utmost importance. In y the rst place the eletcric arc is maintained 'unavoidably lost) is converted into mechanical energy. In other words, drawing out the arc during expansion continually generates new heat, which is simultaneously converted into mechanical energy, and after thevarc breaks andthe generation of heat ceases, f the gases continue to expand and convert heat/ in to mechanical energyu In memes the process carried out in the apparatus of Fig. 2 the further important advantage is obtained of heating `the highest possible proportion of the air, Finally, by making the walls of 'the cylinder of insulating material, and thus preventing ercing between the electrodes and the sides of the cylinder the heating ofthe air to the degree required is absolutely insured.

Having .now fully described my invention, what I `claim and desire to protect by Letters Patent is:

1. The hereinbefore described method of producing oxids of nitrogen from mixtures of oxygen and nitrogen which consists in isolating successive end independent quantities of the mixed gases and within a space having considerable length relatively to its diameter, subjecting each Volume of mixed gases to the influence of .an electric are, drawing out the are in the lengthwise direction of extension of said volume of mixed gases, proportioning the emounto current in the are to the diameter of said volume of mixed gases so as to eect a substantially instantaneous heating of tlie latter to e high temperature end simultaneously theren mixture to expand while drawing out the arc in the direction of extension of tbe volume of gases, and restraining the ere from short crcuiting during the extension.

In testimony of which inventionj "i have hereunto set my hand, at Philadelphia, on this 23rd dey of September., 1912.

FRAN/HS l. on PNT.

Witnesses .l/3.. Hermine it? E. E. WVM 

